In this video, I show you how, for example during a pentest after compromising a user on a Linux machine, you can write your own port scanner in a few minutes to map machines or networks without access to a port scanner, or tools such as telnet or netcat.
A little extra explanation: executing the command on the "pseudo-device" file /dev/tcp/$host/$port opens a TCP connection to the associated socket. That is what enables data transfer here between the machine's network card and other machines on the Internet, a private network, etc.
You can go much further: this also lets you query services directly, grab SSH banners, make WEB requests, etc. For example: http://127.0.0.1:8767/tools/tcp.txt
Complete analysis tools can be built with this method.
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